I have problem on gpu in windows and macos it is working ok but on Zorin i seeing loading screen and login and after login i get crashing and black screen. Sometimes i cannot going to login screen after logo Z and what word is next Z O R I N. Some suggestions?
First suggestion is to name the video card you have. You should know Bourne you have been on tech boards so long 
If you can get to CLI or terminal:
sudo apt install inxi
inxi -GaMSI R9 390 Gaming Specs | TechPowerUp GPU Database here is full specification. Well maybe just gpu memory issue.
If electronics will be damaged then not started propably or if chipset died.
I can trying flashing but it flash a chip gpu bios not a memory.
Besides i ordered another from second hand and we will see.